Disk drives are commonly used in workstations, personal computers, laptops and other computer systems to store large amounts of data that are readily available to a user. In general, a disk drive comprises a magnetic disk that is rotated by a spindle motor. The surface of the disk is divided into a series of data tracks that extend circumferentially around the disk. Each data track can store data in the form of magnetic transitions on the disk surface.
A head includes an interactive element, such as a magnetic transducer, that is used to sense the magnetic transitions to read data, or to generate an electric current that causes a magnetic transition on the disk surface, to write data. The magnetic transducer includes a read/write gap that contains the active elements of the transducer at a position suitable for interaction with the magnetic surface of the disk.
The head further comprises a slider that mounts the transducer to a rotary actuator arm. The actuator arm operates to selectively position the head, including the transducer and slider, over a preselected data track of the disk to either read data from or write data to the preselected data track of the disk, as the disk rotates below the transducer.
The slider is configured to include an air bearing surface that causes the head, and thus the transducer, to fly above the data tracks of the disk surface due to interaction between the air bearing surface of the slider and fluid currents that result from the rotation of the disk. The amount of distance that the transducer flies above the disk surface is referred to as the "fly height." In known disk drive systems, the air bearing surface pivots the slider in the pitch direction and causes the leading edge of the head to rise to a higher level than the trailing edge. Accordingly, the fly height of the head varies from the leading edge to the trailing edge, with the minimum fly height occurring at the trailing edge. The read/write gap is typically mounted at the trailing edge of the slider.
As should be understood, due to operation of the air bearing surface, the transducer does not physically contact the disk surface during normal read and write operation of the disk drive. However, it is generally an objective to achieve an overall fly height that brings the read/write gap of the transducer as close to the disk surface as possible. For example, a Transverse Pressure Contour (TPC) head can be designed to operate at a fly height that is approximately 2.mu. inches above the disk surface.
The closer the active read/write gap of the transducer is brought to the surface of the disk, the stronger the electric signal generated by the transducer due to a magnetic transition on the disk surface which represents data. It is generally advantageous to develop as strong a data signal as possible, to insure reliable electrical performance of the disk drive.
When the disk drive is not operating, the rotation of the storage disk is stopped, and the air bearing surface of the head does not act to cause the transducer to fly. Under such circumstances, the head, including the transducer, comes to rest on the disk surface. Typically, the actuator is operated prior to power down of the disk drive, to position the head over a landing zone provided on the disk surface away from any of the data tracks. In a known contact stop operation of a disk drive, the head comes into contact with the disk surface upon the slowdown and cessation of rotation of the storage disk, after the actuator arm has positioned the head over the landing zone. The use of a landing zone prevents any damage to data tracks that may occur due to contact between the head and the disk surface. However, any contact between the transducer and the disk surface may result in damage to the transducer.
This is particularly true when the disk drive is started again in a contact start operation. A contact start operation causes the commencement of rotation of the disk while the head is still in contact with the landing zone. Stiction between the head and the landing zone, which resists separation between the head and disk surface, can be highly detrimental to the transducer mounted by the head. Indeed, the stiction between the disk surface and the head can be so significant that the air bearing surface cannot lift the head from the disk surface, even at the highest rotational velocity of the disk.
A protective overcoat, such as a layer of carbon, can be applied to each of the disk surface and the air bearing surface of the slider. It has been found that such a protective layer provides significant advantages in protecting the transducer from damage due to contact with the head structures, particularly during contact stop and start operations, leading to a more reliable mechanical performance of the disk drive.
As noted above, the transducer is mounted within the slider at the trailing edge, with the active read/write gap of the transducer exposed at the air bearing surface of the slider. In this manner, the transducer is positioned as close to the disk surface as possible. However, the application of a protective overcoat to the air bearing surface of the slider increases the thickness of the slider below the read/write gap, resulting in an increase in the effective fly height of the read/write gap of the transducer during operation of the disk drive. Accordingly, there is a trade off between improved mechanical performance achieved by the application of a protective coating and diminished electrical performance due an increase in the effective fly height of the read/write gap of the transducer.